Excitation-Wavelength Dependent and Time-Resolved Photoluminescence Studies of Europium Doped GaN Grown by Interrupted Growth Epitaxy (IGE)

The emission properties of Eu doped GaN thin films prepared by interrupted growth epitaxy (IGE) were investigated through excitation-wavelength dependent and time-resolved photoluminescence (PL) studies. Under above-gap excitation (333-363 nm) large differences were observed in the Eu PL intensity and spectral features as a function of Ga shutter cycling time. The overall strongest red Eu PL intensity was obtained from a sample grown with a Gashutter cycling time of 20 minutes. The main Eu emission line originating from D0 ! F2 transition was composed of two peaks located at 620 nm and 622 nm, which varied in relative intensity depending on the growth conditions. The room-temperature emission lifetimes of the samples were non-exponential and varied from ~50 μs to ~200 μs (1/e lifetimes). Under resonant excitation at 471 nm (F0->D2) all samples exhibited nearly identical PL spectra independent of Ga shutter cycling time. Moreover, the Eu PL intensities and lifetimes varied significantly less compared to above-gap excitation. The excitation wavelengths dependent PL results indicate the existence of different Eu centers in GaN: Eu, which can be controlled by the Ga shutter cycling time.